-march=xxx

Sami Virtanen iguchi at pcuf.fi
Tue Jan 23 23:15:39 PST 2001


On Wed, 24 Jan 2001, Jesse Tie Ten Quee wrote:
> On Wed, Jan 24, 2001 at 08:54:05AM +0200, Sami Virtanen wrote:
> > How about config.guess? When you run ./configure, it usually/often guesses
> > (uname -m) your machines architect, I think you know that... anyway I am
> > building LFS-system on another system that where the LFS is heading to. I
> > build it on my Athlon system and when it's ready, I move it on to my
> > server which is running on K6. So, is there any meaning why should I use
> > --host blaablaa, or is it ok that my machine is guessed i686, but when LFS
> > is ready, it will be running on i586?
> 
> uh, running != compiled for.
> 
> Your compiling form the source code and it will either auto detect the
> optimization it should use or use whatever you tell it to, if you
> compile your system and libraries for i686, they will not run on a i586
> or lower (i386/i486).
> 
> If your compiling on a newer/higher-ned box then going to just copy over
> the binaries/files to and older arch (i386/i486/i586), then i would suggest
> using '--host=xxxx-pc-linux-gnu' (where xxxx is the archicture,
> i386/i486/i586) and setting 'export CFLAGS="-march=xxxx"' (and also set
> CXXFLAGS)

Ok, when I build something and do not use CFLAGS, is the code still
optimised, because host is guessed as i686 and gcc gets/uses parametres
like: "-DCPU_...", can't remember that right now, but anyway..? Because
that --host doesn't affect on --march. And what comes to that CFLAGS,
isn't it just dropped away on LFS 2.4.4?

sami


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